Method for transmitting/receiving signal and device therefor

ABSTRACT

The present invention relates to a wireless communication system. More particularly, the present invention relates to a method and a device for a terminal to transmit an uplink signal according to a normal HARQ operation in a wireless communication system supporting a carrier merge, the method comprising the steps of: forming a first cell set with a FDD and a second serving cell set with a TDD; receiving a PHICH signal from a subframe #(n−m−p) of the first serving cell, or receiving a PDCCH signal from a subframe #(n−m) of the first serving cell; and transmitting a PUSCH signal from a subframe #n of the second serving cell, in correspondence to the PHICH signal or the PDCCH signal, wherein n is an integer greater than or equal to 0, m is an integer greater than or equal to 1, and p is an integer greater than or equal to 1.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/005,221, filed on Sep. 13, 2013, now U.S. Pat. No. 9,313,776, whichis the National Stage filing under 35 U.S.C. 371 of InternationalApplication No. PCT/KR2012/001886, filed on Mar. 15, 2012, which claimsthe benefit of U.S. Provisional Application Nos. 61/452,647, filed onMar. 15, 2011, and 61/602,610, filed on Feb. 24, 2012, the contents ofwhich are all incorporated by reference herein in their entirety.

TECHNICAL FIELD

The present invention relates to a wireless communication system, andmore specifically, to a method for transmitting/receiving a signal in asystem simultaneously supporting FDD (Frequency Division Duplex) and TDD(Time Division Duplex) and a device for the same.

BACKGROUND ART

Wireless communication systems have been widely deployed to providevarious types of communication services including voice and dataservices. In general, a wireless communication system is a multipleaccess system that supports communication among multiple users bysharing available system resources (e.g. bandwidth, transmit power,etc.) among the multiple users. The multiple access system may adopt amultiple access scheme such as Code Division Multiple Access (CDMA),Frequency Division Multiple Access (FDMA), Time Division Multiple Access(TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), or SingleCarrier Frequency Division Multiple Access (SC-FDMA).

DISCLOSURE Technical Problem

An object of the present invention devised to solve the problem lies ina method for efficiently transmitting/receiving a signal in a wirelesscommunication system supporting TDD and a device for the same. Anotherobject of the present invention is to provide a method for efficientlytransmitting/receiving a signal in a system simultaneously supportingFDD and TDD and a device for the same.

The technical problems solved by the present invention are not limitedto the above technical problems and those skilled in the art mayunderstand other technical problems from the following description.

Technical Solution

The object of the present invention can be achieved by providing amethod for transmitting an uplink signal by a UE according to a normalHARQ (hybrid automatic repeat and request) operation in a wirelesscommunication system supporting carrier aggregation, the methodincluding: configuring a first cell set to FDD (frequency divisionduplex) and a second cell set to TDD (time division duplex); receiving aPHICH (physical HARQ indicator channel) signal in a subframe #(n−m−p) ofthe first serving cell, or receiving a PDCCH (physical downlink controlchannel) signal in a subframe #(n−m) of the first serving cell; andtransmitting a PUSCH (physical uplink shared channel) signal in asubframe #n of the second cell in response to the PHICH signal or thePDCCH signal, wherein n is an integer greater than or equal to 0, m isan integer greater than or equal to 1, and p is an integer greater thanor equal to 1.

In another aspect of the present invention, provided herein is a UEconfigured to transmit an uplink signal according to a normal HARQoperation in a wireless communication system supporting carrieraggregation, the UE including a radio frequency (RF) unit and aprocessor, wherein the processor is configured to configure a first cellset to FDD and a second cell set to TDD, to receive a PHICH signal in asubframe #(n−m−p) of the first serving cell or receive a PDCCH signal ina subframe #(n−m) of the first serving cell, and to transmit a PUSCHsignal in a subframe #n of the second cell in response to the PHICHsignal or the PDCCH signal, wherein n is an integer greater than orequal to 0, m is an integer greater than or equal to 1, and p is aninteger greater than or equal to 1.

The PHICH signal, the PDCCH signal and the PUSCH signal may correspondto the same HARQ process.

The subframes #(n−m−p), #(n−m) and #n may be allocated to the same HARQprocess.

2m+1 may correspond to an RTT of a HARQ process.

Preferably, m may be 4 and p is 2.

Advantageous Effects

According to the present invention, a signal can be efficientlytransmitted/received in a wireless communication system. Furthermore, asignal can be efficiently transmitted/received in a systemsimultaneously supporting FDD and TDD.

The effects of the present invention are not limited to theabove-described effects and other effects which are not described hereinwill become apparent to those skilled in the art from the followingdescription.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate embodiments of the inventionand together with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 illustrates a radio frame structure;

FIG. 2 illustrates a resource grid of a downlink slot;

FIG. 3 illustrates a downlink subframe structure;

FIG. 4 illustrates an uplink subframe structure;

FIGS. 5 and 6 illustrate TDD UL ACK/NACK (UplinkAcknowledgement/Negative Acknowledgement) transmission timing in asingle cell case;

FIGS. 7 and 8 illustrate TDD PUSCH (Physical Uplink Shared Channel)transmission timing in a single cell case;

FIGS. 9 and 10 illustrate TDD DL ACK/NACK transmission timing in asingle cell case;

FIG. 11 illustrates a TDD HARQ (Hybrid Automatic Repeat reQuest) processin a single cell situation;

FIG. 12 illustrates a carrier aggregation (CA) communication system;

FIG. 13 illustrates scheduling in case of aggregation of a plurality ofcarriers;

FIG. 14 illustrates UL grant timing according to an embodiment of thepresent invention;

FIG. 15 illustrates PHICH (Physical Hybrid Automatic Repeat and reQuestIndicator Channel) timing according to an embodiment of the presentinvention;

FIG. 16 illustrates a HARQ process according to an embodiment of thepresent invention; and

FIG. 17 illustrates a base station (BS) and a user equipment (UE)applicable to an embodiment of the present invention.

BEST MODE

Embodiments of the present invention are applicable to a variety ofwireless access technologies such as Code Division Multiple Access(CDMA), Frequency Division Multiple Access (FDMA), Time DivisionMultiple Access (TDMA), Orthogonal Frequency Division Multiple Access(OFDMA), and Single Carrier Frequency Division Multiple Access(SC-FDMA). CDMA can be implemented as a radio technology such asUniversal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA can beimplemented as a radio technology such as Global System for Mobilecommunications (GSM)/General Packet Radio Service (GPRS)/Enhanced DataRates for GSM Evolution (EDGE). OFDMA can be implemented as a radiotechnology such as Institute of Electrical and Electronics Engineers(IEEE) 802.11 (Wireless Fidelity (Wi-Fi)), IEEE 802.16 (Worldwideinteroperability for Microwave Access (WiMAX)), IEEE 802.20, EvolvedUTRA (E-UTRA). UTRA is a part of Universal Mobile TelecommunicationsSystem (UMTS). 3^(rd) Generation Partnership Project (3GPP) Long TermEvolution (LTE) is a part of Evolved UMTS (E-UMTS) using E-UTRA,employing OFDMA for downlink and SC-FDMA for uplink. LTE-Advanced(LTE-A) is an evolution of 3GPP LTE.

While the following description is given, centering on 3GPP LTE/LTE-A toclarify the description, this is purely exemplary and thus should not beconstrued as limiting the present invention.

FIG. 1 illustrates a radio frame structure.

Referring to FIG. 1, a radio frame used in 3GPP LTE(-A) has a length of10 ms (307200 Ts) and includes 10 subframes in equal size. The 10subframes in the radio frame may be numbered. Here, Ts denotes samplingtime and is represented as Ts=1/(2048*15 kHz). Each subframe has alength of 1 ms and includes two slots. 20 slots in the radio frame canbe sequentially numbered from 0 to 19. Each slot has a length of 0.5 ms.A time for transmitting a subframe is defined as a transmission timeinterval (TTI). Time resources can be discriminated by a radio framenumber (or radio frame index), subframe number (or subframe index) and aslot number (or slot index).

The radio frame can be configured differently according to duplex mode.Downlink transmission is discriminated from uplink transmission byfrequency in FDD (Frequency Division Duplex) mode, and thus the radioframe includes only one of a downlink subframe and an uplink subframe ina specific frequency band.

Particularly, FIG. 1 shows a radio frame structure for TDD, used in 3GPPLTE(-A). Table 1 shows UL-DL configurations of subframes in a radioframe in the TDD mode.

TABLE 1 Downlink- Uplink- to-Uplink downlink Switch- configu- pointSubframe number ration periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U UD S U U U 1 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 ms D S U U U D D D D D 4 10 ms  D S U U D D D D D D 5 10 ms  D S U D D D DD D D 6 5 ms D S U U U D S U U D

In Table 1, D denotes a downlink subframe, U denotes an uplink subframeand S denotes a special subframe. The special subframe includes DwPTS(Downlink Pilot TimeSlot), GP (Guard Period), and UpPTS (Uplink PilotTimeSlot). DwPTS is a period reserved for downlink transmission andUpPTS is a period reserved for uplink transmission. Table 2 showsspecial subframe configuration.

TABLE 2 Normal cyclic prefix in downlink Extended cyclic prefix indownlink Special UpPTS UpPTS subframe Normal Extended Normal Extendedconfigu- cyclic prefix cyclic prefix cyclic prefix cyclic prefix rationDwPTS in uplink in uplink DwPTS in uplink in uplink 0  6592 · T_(s) 2192· T_(s) 2560 · T_(s)  7680 · T_(s) 2192 · T_(s) 2560 · T_(s) 1 19760 ·T_(s) 20480 · T_(s) 2 21952 · T_(s) 23040 · T_(s) 3 24144 · T_(s) 25600· T_(s) 4 26336 · T_(s)  7680 · T_(s) 4384 · T_(s) 5120 · T_(s) 5  6592· T_(s) 4384 · T_(s) 5120 · T_(s) 20480 · T_(s) 6 19760 · T_(s) 23040 ·T_(s) 7 21952 · T_(s) — — — 8 24144 · T_(s) — — —

FIG. 2 illustrates a resource grid of a downlink slot.

Referring to FIG. 2, a downlink slot includes a plurality of OFDMsymbols in the time domain. One downlink slot may include 7(6) OFDMsymbols, and one resource block (RB) may include 12 subcarriers in thefrequency domain. Each element on the resource grid is referred to as aresource element (RE). One RB includes 12×7(6) REs. The number N_(RB) ofRBs included in the downlink slot depends on a downlink transmitbandwidth. The structure of an uplink slot may be same as that of thedownlink slot except that OFDM symbols by replaced by SC-FDMA symbols.

FIG. 3 illustrates a downlink subframe structure.

Referring to FIG. 3, a maximum of three (four) OFDM symbols located in afront portion of a first slot within a subframe correspond to a controlregion to which a control channel is allocated. The remaining OFDMsymbols correspond to a data region to which a physical downlink sharedchancel (PDSCH) is allocated. A PDSCH is used to carry a transport block(TB) or a codeword (CW) corresponding to the TB. The TB means a datablock transmitted from a MAC layer to a PHY layer through a transportchannel. The codeword corresponds to a coded version of a TB. Thecorresponding relationship between the TB and the CW depends on swiping.In the specifically, the PDSCH, TB and CW are interchangeably used.Examples of downlink control channels used in LTE(-A) include a physicalcontrol format indicator channel (PCFICH), a physical downlink controlchannel (PDCCH), a physical hybrid ARQ indicator channel (PHICH), etc.The PCFICH is transmitted at a first OFDM symbol of a subframe andcarries information regarding the number of OFDM symbols used fortransmission of control channels within the subframe. The PHICH is aresponse of uplink transmission and carries an HARQ acknowledgment(ACK)/not-acknowledgment (NACK) signal. A HARQ-ACK response includespositive ACK (simply, ACK), negative ACK (NACK), DTX (DiscontinuousTransmission) or NACK/DTX. Here, HARQ-ACK is used with HARQ ACK/NACK andACK/NACK interchangeably.

Control information transmitted through the PDCCH is referred to asdownlink control information (DCI). The DCI includes resource allocationinformation for a UE or a UE group and other control information. Forexample, the DCI includes uplink/downlink scheduling information, anuplink transmit (Tx) power control command, etc. Transmission modes andinformation content of DCI formats for configuring a multi-antennatechnology are as follows.

Transmission Mode

-   -   Transmission mode 1: Transmission from a single base station        antenna port    -   Transmission mode 2: Transmit diversity    -   Transmission mode 3: Open-loop spatial multiplexing    -   Transmission mode 4: Closed-loop spatial multiplexing    -   Transmission mode 5: Multi-user MIMO    -   Transmission mode 6: Closed-loop rank-1 precoding    -   Transmission mode 7: Transmission using UE-specific reference        signals

DCI Format

-   -   Format 0: Resource grants for the PUSCH transmissions (uplink)    -   Format 1: Resource assignments for single codeword PDSCH        transmissions (transmission modes 1, 2 and 7)    -   Format 1A: Compact signaling of resource assignments for single        codeword PDSCH (all modes)    -   Format 1B: Compact resource assignments for PDSCH using rank-1        closed loop precoding (mod 6)    -   Format 1C: Very compact resource assignments for PDSCH (e.g.        paging/broadcast system information)    -   Format 1D: Compact resource assignments for PDSCH using        multi-user MIMO (mode 5)    -   Format 2: Resource assignments for PDSCH for closed-loop MIMO        operation (mode 4)    -   Format 2A: Resource assignments for PDSCH for open-loop MIMO        operation (mode 3)    -   Format 3/3A: Power control commands for PUCCH and PUSCH with        2-bit/1-bit power adjustments

As described above, the PDCCH may carry a transport format and aresource allocation of a downlink shared channel (DL-SCH), resourceallocation information of an uplink shared channel (UL-SCH), paginginformation on a paging channel (PCH), system information on the DL-SCH,information on resource allocation of an upper-layer control messagesuch as a random access response transmitted on the PDSCH, a set of Txpower control commands on individual UEs within an arbitrary UE group, aTx power control command, information on activation of a voice over IP(VoIP), etc. A plurality of PDCCHs can be transmitted within a controlregion. The UE can monitor the plurality of PDCCHs. The PDCCH istransmitted on an aggregation of one or several consecutive controlchannel elements (CCEs). The CCE is a logical allocation unit used toprovide the PDCCH with a coding rate based on a state of a radiochannel. The CCE corresponds to a plurality of resource element groups(REGs). A format of the PDCCH and the number of bits of the availablePDCCH are determined by the number of CCEs. The BS determines a PDCCHformat according to DCI to be transmitted to the UE, and attaches acyclic redundancy check (CRC) to control information. The CRC is maskedwith a unique identifier (referred to as a radio network temporaryidentifier (RNTI)) according to an owner or usage of the PDCCH. If thePDCCH is for a specific UE, a unique identifier (e.g., cell-RNTI(C-RNTI)) of the UE may be masked to the CRC. Alternatively, if thePDCCH is for a paging message, a paging identifier (e.g., paging-RNTI(P-RNTI)) may be masked to the CRC. If the PDCCH is for systeminformation (more specifically, a system information block (SIB)), asystem information RNTI (SI-RNTI) may be masked to the CRC. When thePDCCH is for a random access response, a random access-RNTI (RA-RNTI)may be masked to the CRC.

FIG. 4 illustrates an uplink subframe structure.

Referring to FIG. 4, an uplink subframe includes a plurality of (e.g. 2)slots. A slot may include different numbers of SC-FDMA symbols accordingto CP lengths. The uplink subframe is divided into a control region anda data region in the frequency domain. The data region is allocated witha PUSCH and used to carry a data signal such as audio data. The controlregion is allocated a PUCCH and used to carry uplink control information(UCI). The PUCCH includes an RB pair located at both ends of the dataregion in the frequency domain and hopped in a slot boundary.

The PUCCH can be used to transmit the following control information.

-   -   SR (scheduling request): This is information used to request a        UL-SCH resource and is transmitted using On-Off Keying (OOK)        scheme.    -   HARQ ACK/NACK: This is a response to a downlink data packet        (e.g. codeword) on a PDSCH and indicates whether the downlink        data packet has been successfully received. A 1-bit ACK/NACK        signal is transmitted as a response to a single downlink        codeword and a 2-bit ACK/NACK signal is transmitted as a        response to two downlink codewords. A HARQ response includes        positive ACK (simply, ACK), negative ACK (NACK), DTX        (Discontinuous Transmission) or NACK/DTX. Here, HARQ-ACK is used        with HARQ ACK/NACK and ACK/NACK interchangeably.    -   CSI (channel state information): This is feedback information        about a downlink channel. MIMO (Multiple Input Multiple        Output)-related feedback information includes a rank indicator        (RI) and a precoding matrix indicator (PMI). 20 bits per        subframe are used.

The quantity of control information (UCI) that a UE can transmit througha subframe depends on the number of SC-FDMA symbols available forcontrol information transmission. The SC-FDMA symbols available forcontrol information transmission mean SC-FDMA symbols except SC-FDMAsymbols of the subframe, which are used for reference signaltransmission. In the case of a subframe in which a Sounding ReferenceSignal (SRS) is configured, the last SC-FDMA symbol of the subframe isexcluded from the SC-FDMA symbols available for control informationtransmission. A reference signal is used to detect coherence of thePUCCH. The PUCCH supports various formats according to informationtransmitted thereon.

Table 3 shows the mapping relationship between PUCCH formats and UCI inLTE(-A).

TABLE 3 PUCCH format UCI (Uplink Control Information) Format 1 SR(Scheduling Request) (non-modulated waveform) Format 1a 1-bit HARQACK/NACK (SR exist/non-exist) Format 1b 2-bit HARQ ACK/NACK (SRexist/non-exist) Format 2 CQI (20 coded bits) Format 2 CQI and 1- or2-bit HARQ ACK/NACK (20 bits) (corresponding to only extended CP) Format2a CQI and 1-bit HARQ ACK/NACK (20 + 1 coded bits) Format 2b CQI and2-bit HARQ ACK/NACK (20 + 2 coded bits) Format 3 Up to 24-bit HARQACK/NACK + SR (LTE-A)

A description will be given of TDD signal transmission timing in asingle carrier (or cell) situation with reference to FIGS. 5 to 11.

FIGS. 5 and 6 illustrate PDSCH-UL ACK/NACK timing. Here, UL ACK/NACKmeans ACK/NACK transmitted on uplink, as a response to DL data (e.g.PDSCH).

Referring to FIG. 5, a UE can receive one or more PDSCH signals in M DLsubframes (SFs) (S502_0 to S502_M−1). Each PDSCH signal is used totransmit one or more (e.g. 2) transport blocks (TBs) according totransmission mode. A PDCCH signal indicating SPS (Semi-PersistentScheduling) release may also be received in step S502_0 to S502_M−1,which is not shown. When a PDSCH signal and/or an SPS release PDCCHsignal is present in the M DL subframes, the UE transmits ACK/NACKthrough a UL subframe corresponding to the M DL subframes via processesfor transmitting ACK/NACK (e.g. ACK/NACK (payload) generation, ACK/NACKresource allocation, etc.) (S504). ACK/NACK includes acknowledgementinformation about the PDSCH signal and/or an SPS release PDCCH receivedin step S502_0 to S502_M−1. While ACK/NACK is transmitted through aPUCCH basically, ACK/NACK is transmitted through a PUSCH when a PUSCH istransmitted at ACK/NACK transmission time. Various PUCCH formats shownin Table 3 can be used for ACK/NACK transmission. To reduce the numberof ACK/NACK bits transmitted through a PUCCH format, various methodssuch as ACK/NACK bundling and ACK/NACK channel selection can be used.

As described above, in TDD, ACK/NACK relating to data received in the MDL subframes is transmitted through one UL subframe (i.e. M DL SF(s): 1UL SF) and the relationship therebetween is determined by a DASI(Downlink Association Set Index).

Table 4 shows DASI (K: {k0, k1, . . . , kM−1}) defined in LTE(-A). Table4 shows spacing between a UL subframe transmitting ACK/NACK and a DLsubframe relating to the UL subframe. Specifically, when a PDCCH thatindicates PDSCH transmission and/or SPS release is present in a subframen−k (k∈K), the UE transmits ACK/NACK in a subframe n.

TABLE 4 TDD UL-DL Configu- Subframe n ration 0 1 2 3 4 5 6 7 8 9 0 — — 6— 4 — — 6 — 4 1 — — 7, 6 4 — — — 7, 6 4 — 2 — — 8, 7, — — — — 8, 7, — —4, 6 4, 6 3 — — 7, 6, 6, 5 5, 4 — — — — — 11 4 — — 12, 8, 6, 5, — — — —— — 7, 11 4, 7 5 — — 13, 12, — — — — — — — 9, 8, 7, 5, 4, 11, 6 6 — — 77 5 — — 7 7 —

FIG. 6 illustrates UL ACK/NACK transmission timing when UL-DLconfiguration #1 is set. In the figure, SF#0 to #9 and SF#10 to #19respectively correspond to radio frames, and numerals in blocks denoteUL subframes relating to DL subframes from the viewpoint of DLsubframes. For example, ACK/NACK for a PDSCH of SF#5 is transmitted inSF#5+7 (=SF#12) and ACK/NACK for a PDSCH of SF#6 is transmitted inSF#6+6 (=SF#12). Accordingly, both ACKs/NACKs for DL signals of SF#5/#6are transmitted in SF#12. Similarly, ACK/NACK for a PDSCH of SF#14 istransmitted in SF#14+4 (=SF#18).

FIGS. 7 and 8 illustrate PHICH/UL grant-PUSCH timing. A PUSCH can betransmitted corresponding to a PDCCH (UL grant) and/or a PHICH (NACK).

Referring to FIG. 7, the UE can receive a PDCCH (UL grant) and/or aPHICH (NACK) (S702). Here, NACK corresponds to an ACK/NACK response toprevious PUSCH transmission. In this case, the UE can initiallytransmit/retransmit one or more TBs through a PUSCH after k subframesvia processes for PUSCH transmission (e.g. TB coding, TB-CW swapping,PUSCH resource allocation, etc.) (S704). The present embodiment is basedon the assumption that a normal HARQ operation in which a PUSCH istransmitted once is performed. In this case, a PHICH and a UL grantcorresponding to PUSCH transmission are present in the same subframe.However, in case of subframe bundling in which a PUSCH is transmittedmultiple times through a plurality of subframes, a PHICH and a UL grantcorresponding to PUSCH transmission may be present in differentsubframes.

Table 5 shows a UAI (Unlink Association Index) (k) for PUSCHtransmission in LTE(-A). Table 5 shows spacing between a DL subframefrom which a PHICH/UL grant is detected and a UL subframe relating tothe DL subframe. Specifically, when a PHICH/UL grant is detected from asubframe n, the UE can transmit a PUSCH in a subframe n+k.

TABLE 5 TDD UL-DL Configu- subframe number n ration 0 1 2 3 4 5 6 7 8 90 4 6 4 6 1 6 4 6 4 2 4 4 3 4 4 4 4 4 4 5 4 6 7 7 7 7 5

FIG. 8 illustrates PUSCH transmission timing when UL-DL configuration #1is set. In the figure, SF#0 to #9 and SF#10 to #19 respectivelycorrespond to radio frames, and numerals in blocks denote UL subframesrelating to DL subframes from the viewpoint of DL subframes. Forexample, a PUSCH corresponding to PHICH/UL grant of SF#6 is transmittedin SF#6+6 (=SF#12) and a PUSCH corresponding to a PHICH/UL grant ofSF#14 is transmitted in SF#14+4 (=SF#18).

FIGS. 9 and 10 illustrate PUSCH-PHICH/UL grant timing. A PHICH is usedto transmit DL ACK/NACK. Here, DL ACK/NACK means ACK/NACK transmitted ondownlink as a response to UL data (e.g. PUSCH).

Referring to FIG. 9, the UE transmits a PUSCH signal to the BS (S902).Here, the PUSCH signal is used to transmit one or a plurality of (e.g.2) TBs according to transmission mode. The BS can transmit ACK/NACK as aresponse to PUSCH transmission through a PHICH after k subframes viaprocesses for ACK/NACK transmission (e.g. ACK/NACK generation, ACK/NACKresource allocation, etc.) (S904). ACK/NACK includes acknowledgementinformation about the PUSCH signal of step S902. When a response toPUSCH transmission is NACK, the BS can transmit a UL grant PDCCH forPUSCH retransmission to the UE after k subframe (S904). The presentembodiment is based on the assumption that a normal HARQ operation inwhich a PUSCH is transmitted once is performed. In this case, a PHICH/ULgrant used for PUSCH transmission can be transmitted in the samesubframe. In case of subframe bundling, however, the PHICH and UL grantused for PUSCH transmission can be transmitted in different subframes.

Table 6 shows a UAI (k) for PHICH/UL grant transmission in LTE(-A).Table 6 shows spacing between a DL subframe in which a PHICH/UL grant ispresent and a UL subframe relating to the DL subframe. Specifically, aPHICH/UL grant of a subframe i corresponds to PUSCH transmission througha subframe i−k.

TABLE 6 TDD UL-DL Configu- subframe number i ration 0 1 2 3 4 5 6 7 8 90 7 4 7 4 1 4 6 4 6 2 6 6 3 6 6 6 4 6 6 5 6 6 6 4 7 4 6

FIG. 10 illustrates PHICH/UL grant transmission timing when UL-DLconfiguration #1 is set. In the figure, SF#0 to #9 and SF#10 to #19respectively correspond to radio frames, and numerals in blocks denoteDL subframes relating to UL subframes from the viewpoint of ULsubframes. For example, a PHICH/UL grant corresponding to a PUSCH ofSF#2 is transmitted in SF#2+4 (=SF#6) and a PHICH/UL grant correspondingto a PUSCH of SF#8 is transmitted in SF#8+6 (=SF#14).

PHICH resource allocation will now be described. When a PUSCH istransmitted in subframe #n, the UE determines a PHICH resourcecorresponding to the PUSCH in subframe #(n+k_(PHICH)). In case of FDD,k_(PHICH) has a fixed value (e.g. 4). In case of TDD, k_(PHICH) has avalue depending on UL-DL configuration. Table 7 shows k_(PHICH) for TDDis equivalent to Table 6.

TABLE 7 TDD UL-DL Configu- UL subframe index n ration 0 1 2 3 4 5 6 7 89 0 4 7 6 4 7 6 1 4 6 4 6 2 6 6 3 6 6 6 4 6 6 5 6 6 4 6 6 4 7

A PHICH resource is provided by [PHICH group index, orthogonal sequenceindex]. The PHICH group index and the orthogonal sequence index aredetermined using (i) a lowest PRB index used for PUSCH transmission and(ii) a 3-bit field value for DMRS (Demodulation Reference Signal) cyclicshift. Here, (i) and (ii) are indicated by a UL grant PDCCH.

A description will be given of a HARQ process. The UE executes aplurality of parallel HARQ processes for UL transmission. The pluralityof parallel HARQ processes are used to continuously perform ULtransmission while the UE waits for HARQ feedback representing whetherprevious UL transmission has been successful or not. Each HARQ processrelates to a HARQ buffer of a MAC (Medium Access Control) layer. EachHARQ process manages the number of transmissions of a MAC PDU (PhysicalData Unit) in the buffer, HARQ feedback for the MAC PDU in the buffer,and a state parameter regarding a current redundancy version.

In case of LTE(-A) FDD, the number of UL HARQ processes for non-subframebundling operation (i.e. normal HARQ operation) is 8. In case of LTE(-A)TDD, the number of UL HARQ processes is set differently according toDL-UL configurations. When subframe bundling is applied, a bundle ofPUSCHs configured of 4 contiguous UL subframes is transmitted in FDD andTDD. Accordingly, a HARQ operation/process when subframe bundling isapplied is different from the normal HARQ operation/process.

Table 8 shows the number of synchronous UL HARQ processes in TDD.

TABLE 8 TDD UL-DL Number of HARQ Number of HARQ configu- processes fornormal processes for subframe ration HARQ operation bundling operation 07 3 1 4 2 2 2 N/A 3 3 N/A 4 2 N/A 5 1 N/A 6 6 3

In case of TDD UL-DL configurations #1 to #6 and normal HARQ operation,the UE transmits a corresponding PUSCH signal in subframe n+k (refer toTable 5) according to UL grant PDCCH and/or PHICH information upondetection of the UL grant PDCCH and/or PHICH information in subframe n.

In case of TDD UL-DL configuration #0 and the normal HARQ operation,when a UL DCI grant PDCCH and/or a PHICH are detected from subframe n,PUSCH transmission timing of the UE is varied according to conditions.When the MSB (Most Significant bit) of a UL index in DCI is 1 or thePHICH is received through a resource corresponding to I_(PHICH)=0 insubframe #0 or #5, the UE transmits the corresponding PUSCH signal insubframe n+k (refer to Table 5). When the LSB (Least Significant bit) ofthe UL index in the DCI is 1, the PHICH is received through a resourcecorresponding to I_(PHICH)=1 in subframe #0 or #5, or the PHICH isreceived in subframe #1 or #6, UE transmits the corresponding PUSCHsignal in subframe n+7. When both the MSB and LSB in the DCI are set,the UE transmits the corresponding PUSCH signal in subframe n+k (referto Table 5) and subframe n+7.

FIG. 11 illustrates a synchronous UL HARQ process when UL-DLconfiguration #1 is set. Numerals in blocks denote UL HARQ processnumbers. The synchronous UL HARQ process shown in FIG. 11 corresponds toa normal HARQ process. Referring to FIG. 11, HARQ process #1 involvesSF#2, SF#6, SF#12 and SF#16. For example, if an initial PUSCH signal(e.g. RV=0) is transmitted in SF#2, a UL grant PDCCH and/or a PHICHcorresponding to the PUSCH signal can be received in SF#6 and a(retransmission) PUSCH signal (e.g. RV=2) corresponding to the initialPUSCH signal can be transmitted in SF#12. Accordingly, 4 UL HARQprocesses having an RTT (Round Trip Time) of 10 SFs (or 10 ms) arepresent in case of UL-DL configuration #1.

FIG. 12 illustrates a carrier aggregation (CA) communication system. Touse a wider frequency band, an LTE-A system employs CA (or bandwidthaggregation) technology which aggregates a plurality of UL/DL frequencyblocks to obtain a wider UL/DL bandwidth. Each frequency block istransmitted using a component carrier (CC). The CC can be regarded as acarrier frequency (or center carrier, center frequency) for thefrequency block.

Referring to FIG. 12, a plurality of UL/DL CCs can be aggregated tosupport a wider UL/DL bandwidth. The CCs may be contiguous ornon-contiguous in the frequency domain. Bandwidths of the CCs can beindependently determined. Asymmetrical CA in which the number of UL CCsis different from the number of DL CCs can be implemented. For example,when there are two DL CCs and one UL CC, the DL CCs can correspond tothe UL CC in the ratio of 2:1. A DL CC/UL CC link can be fixed orsemi-statically configured in the system. Even if the system bandwidthis configured with N CCs, a frequency band that a specific UE canmonitor/receive can be limited to M (<N) CCs. Various parameters withrespect to CA can be set cell-specifically, UE-group-specifically, orUE-specifically. Control information may be transmitted/received onlythrough a specific CC. This specific CC can be referred to as a PrimaryCC (PCC) (or anchor CC) and other CCs can be referred to as SecondaryCCs (SCCs).

In LTE-A, the concept of a cell is used to manage radio resources. Acell is defined as a combination of downlink resources and uplinkresources. Yet, the uplink resources are not mandatory. Therefore, acell may be composed of downlink resources only or both downlinkresources and uplink resources. The linkage between the carrierfrequencies (or DL CCs) of downlink resources and the carrierfrequencies (or UL CCs) of uplink resources may be indicated by systeminformation. A cell operating in primary frequency resources (or a PCC)may be referred to as a primary cell (PCell) and a cell operating insecondary frequency resources (or an SCC) may be referred to as asecondary cell (SCell). The PCell is used for a UE to establish aninitial connection or re-establish a connection. The PCell may refer toa cell operating on a DL CC SIB2-linked to a UL CC. Furthermore, thePCell may refer to a cell indicated during handover. The SCell may beconfigured after an RRC connection is established and may be used toprovide additional radio resources. The PCell and the SCell maycollectively be referred to as a serving cell. Accordingly, a singleserving cell composed of a PCell only exists for a UE in anRRC_Connected state, for which CA is not set or which does not supportCA. On the other hand, one or more serving cells exist, including aPCell and entire SCells, for a UE in an RRC_CONNECTED state, for whichCA is set. For CA, a network may configure one or more SCells inaddition to an initially configured PCell, for a UE supporting CA duringconnection setup after an initial security activation operation isinitiated.

FIG. 13 illustrates scheduling when a plurality of carriers isaggregated. It is assumed that 3 DL CCs are aggregated and DL CC A isset to a PDCCH CC. DL CC A, DL CC B and DL CC C can be called servingCCs, serving carriers, serving cells, etc. In case of CIF (CarrierIndicator Field) disabled, a DL CC can transmit according to the PDCCHrules only a PDCCH that schedules a PDSCH corresponding to the DL CCwithout a CIF (non-cross-CC scheduling). When the CIF is enabledaccording to UE-specific (or UE-group-specific or cell-specific) higherlayer signaling, a specific CC (e.g. DL CC A) can transmit not only aPDCCH that schedules the PDSCH corresponding to the DL CC A but alsoPDCCHs that schedule PDSCHs of other DL CCs using the CIF (cross-CCscheduling). A PDCCH is not transmitted in DL CC B/C.

A specific CC (or cell) used for PDCCH transmission is called ascheduling CC (or scheduling cell). The scheduling CC (or cell) may beused with a monitoring CC interchangeably. A CC (or cell) in which aPDSCH/PUSCH is scheduled by a PDCCH of another CC is called a scheduledCC (or scheduled cell). One or more scheduling CCs may be set for one UEand one of the scheduling CCs may be used for DL control signaling andUL PUCCH transmission. That is, a scheduling CC includes a PCC. Whenonly one scheduling CC is set, the scheduling CC corresponds to the PCC.

When cross-CC scheduling is set, CCs carrying signals are definedaccording to signal type as follows.

-   -   PDCCH (UL/DL grant): scheduling CC    -   PDSCH/PUSCH: CC indicated by a CIF of a PDCCH, detected from a        scheduling CC    -   DL ACK/NACK (e.g. PHICH): scheduling CC (e.g. DL PCC)    -   UL ACK/NACK (e.g. PUCCH): UL PCC

A conventional CA system considers only a case in which all aggregatedCCs operate in the same duplex mode (i.e. FDD or TDD). In addition, theconventional CA system considers only a case in which all aggregated CCshave the same UL-DL configuration when operating in a TDD mode.Accordingly, signal (e.g. UL grant, PHICH, etc.) transmission/receptiontiming during cross-CC scheduling has no problem because all CCs havethe same DL/UL transmission timing in the conventional CA system.

A system following LTE-A considers aggregation of a plurality of CCsoperating according to different duplexing schemes. For example, a DL/ULCC pair operating in FDD can be set as a DL/UL PCC pair and a CCoperating in TDD can be set as an SCC for optimization of DL/UL controlsignaling. In this case, DL/UL transmission timing of a CC (e.g. PCC)operating in FDD is different from that of a CC operating in TDD, andthus signal transmission/reception timing may have problems duringcross-CC scheduling.

To solve this problem, the present invention proposes a method forsetting signal transmission timing when an FDD CC and a TDD CC areaggregated. In addition, the present invention proposes a HARQ processwhen an FDD CC and a TDD CC are aggregated.

While embodiments of the present invention will be described below onthe assumption that two CCs (i.e. an FDD PCC and a TDD SCC) configuredto different duplex are aggregated, the embodiments of the presentinvention can also be applied to a case in which three or more CCs areaggregated and a scheduling CC and a scheduled CC have different duplexmodes. In this case, the embodiments of the present invention can becommonly applied to all aggregated CCs, commonly applied to only CC(s)on which cross-CC scheduling is performed, or independently applied to aCC pair (i.e. a scheduling CC and a scheduled CC). Furthermore, theembodiments of the present invention can be applied to aggregation of CCgroups having different duplex modes in the same or similar manner.Here, a CC group may include one or more CCs or CC pairs.

It is assumed that a PCC corresponds to a scheduling CC and an SCCcorresponds to a scheduled CC in the following description. In addition,it is assumed that the PCC operates in FDD and the SCC operates in TDD.However, this assumption is exemplary and the PCC can operate in TDD andthe SCC can operate in FDD. In case of FDD based CC, DL refers to a DLCC and UC refers to a UL CC. Accordingly, PCC DC may refer to a PCC DLCC and PCC UC may refer to a PCC UL CC. In case of TDD based CC, Drefers to a DL subframe (SF) or special SF and U refers to a UL SF.Accordingly, SCC D may refer to a DL SF or special SF on an SCC and SCCU may refer to a UL SF on an SCC.

In the following description, “CC” can be used interchangeably with“cell” (or “serving cell”), “PCC” can be used interchangeably with“PCell”, and “SCC” can be used interchangeably with “SCell”. While acase in which a signal transmission/reception process is performed by aUE is described in the following, this signal transmission/receptionprocess can be applied when a BS (or relay) replaces the UE, except thatthe UE signal transmission/reception direction is changed.

Embodiment 1: UL Grant Transmission

First, UL grant timing is defined. The UL grant timing may refer to atiming relationship between a UL grant and a PUSCH. For example, the ULgrant timing can be defined as a timing interval (unit: SF or ms, forexample) between the UL grant and the PUSCH. It is assumed that the ULgrant timing is g SF(s) for description. In this case, when the UL grantis received in SF #h, the PUSCH corresponding to the UL grant istransmitted in SF #(h+g). Conversely, when the PUSCH is transmitted inSF #h, the corresponding UL grant is received in SF #(h−g). In a narrowsense, the UL grant timing may refer to UL grant reception timingcorresponding to PUSCH transmission. For example, when a PUSCH signal istransmitted in SF #h, the UL grant timing can correspond to SF #(h−g).Accordingly, the UL grant timing can refer to the timing relationshipbetween the UL grant and PUSCH or UL grant transmission/reception time.

In case of FDD based single CC, UL grant timing with respect to a PUSCHtransmitted on a UC through SF #h can be fixed to SF #(h−m). Here, m maydenote a minimum SF interval (e.g. 4 SFs or 4 ms) between UL grantreception timing and PUSCH transmission timing in response thereto. Incase of TDD based single CC, UL grant timing for a PUSCH transmitted ona CC through UL SF #h can be set as DL SF #(h−k_(UG)) in the same CC.TDD UL grant timing can refer to FIGS. 7 and 8. Here, k_(UG) can beprovided on the basis of a UL SF, in which the PUSCH is transmitted, ordefined on the basis of a DL SF, in which the UL grant is received. Whenk_(UG) is defined on the basis of the DL SF in which the UL grant isreceived, it can be given as shown in Table 5.

A description will be given of a method for setting UL grant timing whencross-CC scheduling is set in CA based on different duplex modes. Thepresent embodiment is based on the assumption that a PCC operates in FDDand an SCC operates in TDD. Accordingly, DL/UL is present for the PCCfor each SF, and UL SF timing is defined for the SCC according to UL-DLconfiguration (Table 1).

According to the present embodiment, fixed FDD UL grant timing can beapplied to PUSCH transmission (referred to as PCC PUSCH hereinafter) ona PCC UC (i.e. non-cross-CC scheduling). That is, when a PUSCH istransmitted on the PCC UC through SF #h, a UL grant correspondingthereto can be received in SF #(h−m) (e.g. m=4) of a PCC DC. For a PUSCH(referred to as SCC PUSCH) transmitted through U (SF #n) of an SCCaccording to cross-CC scheduling, the following scheme for setting ULgrant timing on a PCC DC can be considered.

(1) Method 1-1: FDD UL grant timing (e.g. PCC UL grant timing) can beapplied to an SCC PUSCH on a TDD CC. For example, when a PUSCH istransmitted through U (SF #n) of an SCC, a corresponding UL grant can bereceived through SF #(n−m) of a PCC DC. According to the method of thepresent embodiment, a delay between the UL grant and PUSCH correspondingthereto can be reduced when the TDD CC operates.

(2) Method 1-2: TDD UL grant timing (e.g. SCC UL grant timing) can beapplied to an SCC PUSCH on a TDD CC. For example, when a PUSCH istransmitted through U (SF #n) of an SCC, a corresponding UL grant can bereceived through SF #(n−k_(UG)) of a PCC DC. Here, k_(UG) is providedaccording to TDD UL-DL configuration (refer to Table 5). According tothe method of the present embodiment, existing UL grant-PUSCH timing setaccording to DL-UL configuration can be reused.

In case of Method 1-2, when a PCC DC includes a UL grant PDCCH, the BSand UE need to set timing of transmitting a PUSCH corresponding to thePDCCH differently according to non-cross-CC scheduling or cross-CCscheduling. To achieve this, the BS and UE can determine UL grant timingusing a CIF value of the UL grant PDCCH. For example, the UL granttiming can be determined using m when the CIF value indicates a PCC anddetermined using k_(UG) when the CIF value indicates an SCC.

FIG. 14 illustrates UL grant timing according to Methods 1-1 and 1-2.FIG. 14 shows a case in which a PCC and an SCC respectively operate inFDD and TDD DL-UL configuration #6 (Table 1). A numeral affixed to a PCCDC denotes FDD UL grant timing (i.e. m=4) and a numeral affixed to D ofthe SCC denotes TDD UL grant timing (i.e. k_(UG)) (refer to Table 5).According to Method 1-1, when a PUSCH is transmitted through SF #12 ofthe SCC, a UL grant corresponding to the PUSCH can be received through aPCC DC in SF #(12−4)=SF #8 according to FDD UL grant timing (m=4) set toa PCC UC in SF #12 (refer to FIG. 14(a)). According to Method 1-2, whena PUSCH is transmitted in SF #12 of the SCC, a UL grant corresponding tothe PUSCH can be received through a PCC DC in SF #(12−7)=SF #5 accordingto TDD UL grant timing (i.e. k_(UG)=7) set to U of the SCC in SF #12(refer to FIG. 14(b)).

In case of Method 1-1, UL grant timing need not be defined in an SF(e.g. SF #(d−m)) of a PCC DC corresponding to a D of SCC(e.g. SF #d).Accordingly, the BS does not transmit a UL grant for an SCC in an SF ofa PCC DC corresponding to a D of SCC, and thus the UE can attempt toperform blind decoding to receive a PDCCH. For example, the UE can omita blind decoding process with respect to a UL DCI format (PUSCHscheduling information) in a search space for the SCC. Here, the searchspace refers to a resource (area) including a plurality of PDCCHcandidates that need to be monitored by the UE. Specifically, the UE canomit an operation (e.g. blind decoding) for receiving a DCI format for aUL grant in SF #(10N+1), SF #(10N+2), SF #(10N+5), SF # (10N+6) and SF#(10N+7) of PCC DC in FIG. 14(a). Furthermore, if the SCC corresponds toU in SF #(d−m), the BS can omit even DL grant transmission for the SCC.In this case, the UE can skip a PDCCH reception process (e.g. blinddecoding) for the SCC in SF #(d−m) of PCC DC. For example, the UE canskip monitoring of the search space for the SCC in SF #(d−g) of PCC DC.Specifically, the UE can skip a PDCCH reception operation (e.g. blinddecoding) for the SCC in SF #(10N+2) and SF #(10N+7) of PCC DC in FIG.14(a). Here, N is an integer greater than 0.

In case of Method 1-2, since UL grant timing is determined based on D ofSCC, a UL grant for an SCC PUSCH can be received only in a subframe(e.g. SF #d) in which the SCC corresponds to D. Accordingly, the BS maynot transmit the UL grant for the SCC through PCC DC in a subframe inwhich the SCC corresponds to U, and thus the UE can attempt to performblind decoding to receive a PDCCH. For example, the UE can skip a blinddecoding process with respect to a UL DCI format (PUSCH schedulinginformation) in a search space for the SCC. Furthermore, the BS may nottransmit a DL grant for the SCC through PCC DC in the subframe in whichthe SCC corresponds to U. Accordingly, the UE can skip a PDCCH receptionprocess (e.g. blind decoding) for the SCC in the subframe in which theSCC corresponds to U. For example, the UE can skip monitoring of thesearch space for the SCC through PCC DC in the subframe in which the SCCcorresponds to U. Specifically, the UE can omit a PDCCH receptionprocess (e.g. blind decoding) for the SCC in SF #(10N+2), SF #(10N+3),SF #(10N+4), SF #(10N+7) and SF #(10N+8) of PCC DC in FIG. 14(b).

Embodiment 2: PHICH Transmission

PHICH timing is defined. The PHICH timing may refer to a timingrelationship between a PUSCH and a PHICH. For example, the PHICH timingcan be defined as a timing interval (unit: SF or ms, for example)between the PUSCH and the PHICH. It is assumed that the PHICH timing isp SF(s) for description. In this case, when the PUSCH is transmitted inSF #h, the PHICH corresponding to the PUSCH is received in SF #(h+p).Conversely, when the PHICH is received in SF #h, the corresponding PUSCHis transmitted in SF #(h−p). In a narrow sense, the PHICH timing mayrefer to PHICH reception timing corresponding to PUSCH transmission. Forexample, when a PUSCH signal is transmitted in SF #h, the PHICH timingcan correspond to SF #(h+p). Accordingly, the PHICH timing can refer tothe timing relationship between the PUSCH and PHICH or PHICHtransmission/reception time.

In case of FDD based single CC, PHICH timing with respect to a PUSCHtransmitted on a UC through SF #h can be fixed to SF #(h+m). Here, m maydenote a minimum SF interval (e.g. 4 SFs or 4 ms) between PUSCHtransmission and PHICH reception in response thereto. In case of TDDbased single CC, PHICH timing for a PUSCH transmitted through UL SF #hcan be set as DL SF #(h+k_(PHICH)). TDD PHICH timing can refer to FIGS.9 and 10, and k_(PHICH) can be provided as shown in Table 7.

A description will be given of a method for setting PHICH timing whencross-CC scheduling is set in CA based on different duplex modes. Thepresent embodiment is based on the assumption that a PCC operates in FDDand an SCC operates in TDD. Accordingly, DL/UL is present for the PCCfor each SF, and UL SF timing is defined for the SCC according to UL-DLconfiguration (Table 1).

According to the present embodiment, fixed FDD PHICH timing can beapplied to PUSCH transmission (referred to as PCC PUSCH hereinafter) ona PCC UC (i.e. non-cross-CC scheduling). That is, when a PUSCH istransmitted on the PCC UC through SF #h, a PHICH corresponding theretocan be received in SF #(h+m) (e.g. m=4) of a PCC DC. For a PUSCH(referred to as SCC PUSCH) transmitted through U (SF #n) of an SCCaccording to cross-CC scheduling, the following scheme for setting PHICHtiming on a PCC DC can be considered.

(1) Method 2-1: FDD PHICH timing (e.g. PCC PHICH timing) can be appliedto an SCC PUSCH on a TDD CC. For example, when a PUSCH is transmittedthrough U (SF #n) of an SCC, a corresponding PHICH can be receivedthrough SF #(n+m) of a PCC DC. According to the method of the presentembodiment, a delay caused by DL ACK/NACK feedback for TDD based PUSCHtransmission can be reduced.

(2) Method 2-2: TDD PHICH timing (e.g. SCC PHICH timing) can be appliedto an SCC PUSCH on a TDD CC. For example, when a PUSCH is transmittedthrough U (SF #n) of an SCC, a corresponding PHICH can be receivedthrough SF #(n+k_(PHICH)) of a PCC DC. Here, k_(PHICH) is providedaccording to TDD UL-DL configuration (refer to Table 7). According tothe method of the present embodiment, existing HARQ processing timingset according to DL-UL configuration can be reused.

A PHICH resource is determined using a lowest PRB index used for PUSCHtransmission. Accordingly, PHICH resources may collide when a PUSCHtransmitted through an SCC U in SF #n and a PUSCH transmitted through aPCC UC in SF #(n+k_(PHICH)−4) use the same lowest PRB index in Method2-2. To prevent collision of PHICH resources, a PHICH resourcecorresponding to an SCC PUSCH can be modified using an offset value todetermine the PHICH resource. For example, the offset value can beincluded as a parameter in an equation for determining a PHICH resourceindex or applied in the form of PHICH resource index+offset.

FIG. 15 illustrates PHICH timing according to Methods 2-1 and 2-2. FIG.15 shows a case in which a PCC and an SCC respectively operate in FDDand TDD DL-UL configuration #1 (Table 1). A numeral affixed to a PCC UCdenotes FDD PHICH timing (i.e. m=4) and a numeral affixed to U of theSCC denotes TDD PHICH timing (i.e. k_(PHICH)) (refer to Table 7).According to Method 2-1, when a PUSCH is transmitted through an SCC U inSF #8, a PHICH corresponding to the PUSCH can be received through a PCCDC in SF #(8+4)=SF #12 according to FDD PHICH timing set to PCC DC in SF#8 (refer to FIG. 15(a)). According to Method 2-2, when a PUSCH istransmitted in SF #8 through U of SCC, a PHICH corresponding to thePUSCH can be received through a PCC DC in SF #(8+6)=SF #14 according toTDD PHICH timing set to U of SCC in SF #8 (refer to FIG. 15 (b)).

Embodiment 3: HARQ Process

Considering UL grant timing/PHICH timing described above with referenceto FIGS. 7 to 10, a PHICH and UL grant corresponding to the samesubframe are allocated to the same HARQ process in a conventional normalHARQ operation. For example, a normal HARQ process in FDD is composed of(initial transmission) PUSCH (SF #n)=>PHICH/UL (retransmission) grant(SF #(n+4))=>(retransmission) PUSCH (SF #(n+8)). Similarly, a normalHARQ process in TDD is composed of (initial transmission) PUSCH (SF#n)=>PHICH/UL (retransmission) grant (SF#(n+k_(PHICH))=>(retransmission) PUSCH (SF #(n+k_(PHICH)±k_(UG))). Here,k_(PHICH) and k_(UG) respectively correspond to PHICH timing and ULgrant timing.

Accordingly, considering a case to which both Method 1-1 (FDD UL granttiming) and Method 2-1 (FDD PHICH timing) are applied, a HARQ processfor a PUSCH (e.g. SCC PUSCH) of a TDD CC can be composed of (initialtransmission) SCC PUSCH (SF #n)=>PCC PHICH/UL (retransmission) grant (SF#(n+4)=>(retransmission) SCC PUSCH (SF #(n+8)). That is, in case of theTDD CC, RTT (Round Trip time) of a UL HARQ process can be set as 8 SFs(or ms).

However, it may be efficient to set the RTT of the UL HARQ process as 10SFs (or ms) or a multiple of 10 SFs (or ms), for example, consideringthat the TDD SF structure is repeated in the unit of 10 SFs (or ms) andthus the RTT of the UL HARQ process is normally set as 10 SFs (or ms) inTDD. The present embodiment proposes a UL HARQ process configurationscheme in case of TDD CC. The present embodiment is based on theassumption that a PCC operates in FDD and an SCC operates in TDD. Thepresent embodiment exemplifies a normal HARQ process. A HARQ processwhen subframe bundling is applied is explicitly excluded from the rangeof the present embodiment.

Specifically, the present embodiment proposes allocation of UL SF#(10N+n) of an SCC PUSCH and SF #(10N+n+m) corresponding to PCC PHICHtiming with respect to UL SF #(10N+n) (Method 1-1), and UL SF #(10(N+1)+n) of the SCC PUSCH and SF #(10(N+1)+n−m) corresponding to PCC ULgrant timing with respect to UL SF #(10(N+1)+n) (Method 1-2) to the sameUL HARQ process (N=0, 1, . . . ). For example, a UL HARQ process for theSCC can be composed of (initial transmission) SCC PUSCH [SF #n]=>PCCPHICH [SF #(n+m)]=>PCC UL (retransmission) grant [SF#(10+n+m)]=>(retransmission) SCC PUSCH [SF #(10+n)]. Here, m can be setas 4. That is, the present embodiment intentionally provides a timedifference of 2 (=(10−2m)) SFs (or ms) between PCC PHICH timing=>PCC ULgrant timing in order to set the RTT of the UL HARQ process to 10 SFs(or ms) for the SCC. The number of PUSCH HARQ processes allocated to TDDCC may be set to be equal to the number of UL SFs within 10 SFs (or ms)of Table 1.

The present embodiment is based on the assumption that the RTT of the ULHARQ process with respect to the TDD CC is set as 10 SFs (or ms).However, the RTT of the UL HARQ process in the TDD CC may be greaterthan 10 SFs (or ms) according to TDD UL-DL configuration or design.Accordingly, the UL HARQ process can be normalized as follows.(Initial transmission) SCC PUSCH [SF #(R*N+n)]=>PCC PHICH [SF#(R*N+n+mPHICH)]=>PCC UL (retransmission) grant [SF#(R*(N+1)+n−mUG)]=>(retransmission) SCC PUSCH [SF #(R*(N+1)+n)]

Here, R denotes the RTT of the UL HARQ process. R is a positive integer.For example, R can be a multiple of 10. N and n are integers greaterthan 0. mPHICH and mUG respectively correspond to PHICH timing and ULgrant timing and are integers greater than 1. mPHICH and mUG may beidentical or may be independently defined. Preferably, both mPHICH andmUG can be defined as 4.

FIG. 16 illustrates an example of setting UL grant timing and PHICHtiming for PUSCH scheduling of a TDD CC (e.g. SCC) according to thepresent embodiment. The example shows a case in which the SCCcorresponds to UL-DL configuration #1 (Table 1). In case of UL-DLconfiguration #1, 4 UL SFs are included in 10 [SFs or ms], and thus thenumber of UL HARQ processes allocated to the SCC can be set to 4.

Referring to FIG. 16, UX (PUSCH timing), PX (PHICH timing) and GX (ULgrant timing) represent a timing set allocated to UL HARQ process #X.Here, X is an integer indicating a HARQ process index. For example, SCCU (U1) of SF #2, PCC DC (P1) of SF #6, PCC DC (G1) of SF #8, and SCC U(U1) of SF #12 can be allocated to UL HARQ process #1. Accordingly, aPUSCH can be transmitted through an SCC U corresponding to SF #2 and aPHICH corresponding to the PUSCH can be received through a PCC DCcorresponding to SF #6. Furthermore, a (retransmission) UL grant can bereceived through a PCC DC corresponding to SF #8 and a (retransmission)PUSCH corresponding thereto can be transmitted through an SCC Ucorresponding to SF #12 in the same UL HARQ process. When the UEreceives a PHICH through the PCC DC corresponding to SF #6(=#n−6) and/orreceives a UL grant through the PCC DC corresponding to SF #8(=#n−4), aPUSCH is transmitted through an SCC U corresponding to SF #12 (=#n).Whether the PUSCH is initially transmitted or retransmitted can bedetermined according to whether the PHICH has been received and thecontents of the UL grant (e.g. whether an NDI (New Data Indicator) hasbeen toggled).

FIG. 17 illustrates a BS and a UE applicable to an embodiment of thepresent invention. When a wireless communication system includes arelay, communication is performed between a BS and the relay on abackhaul link and between the relay and a UE on an access link. The BSor UE shown in FIG. 16 can be replaced by a relay as necessary.

Referring to FIG. 17, an RF communication system includes a BS 110 and aUE 120. The BS 110 includes a processor 112, a memory 114 and an RF unit116. The processor 112 may be configured to implement the proceduresand/or methods proposed by the present invention. The memory 114 isconnected to the processor 112 and stores various types of informationrelating to operations of the processor 112. The RF unit 116 isconnected to the processor 112 and transmits and/or receives RF signals.The UE 120 includes a processor 122, a memory 124 and an RF unit 126.The processor 122 may be configured to implement the procedures and/ormethods proposed by the present invention. The memory 124 is connectedto the processor 122 and stores various types of information relating tooperations of the processor 122. The RF unit 126 is connected to theprocessor 122 and transmits and/or receives RF signals. The BS 110 andthe UE 120 may have a single antenna or multiple antennas.

The embodiments of the present invention described hereinbelow arecombinations of elements and features of the present invention. Theelements or features may be considered selective unless otherwisementioned. Each element or feature may be practiced without beingcombined with other elements or features. Further, an embodiment of thepresent invention may be constructed by combining parts of the elementsand/or features. Operation orders described in embodiments of thepresent invention may be rearranged. Some constructions of any oneembodiment may be included in another embodiment and may be replacedwith corresponding constructions of another embodiment. It is obvious tothose skilled in the art that claims that are not explicitly cited ineach other in the appended claims may be presented in combination as anembodiment of the present invention or included as a new claim by asubsequent amendment after the application is filed.

In the embodiments of the present invention, a description is made,centering on a data transmission and reception relationship between a BSand a UE. In some cases, a specific operation described as performed bythe BS may be performed by an upper node of the BS. Namely, it isapparent that, in a network comprised of a plurality of network nodesincluding a BS, various operations performed for communication with anMS may be performed by the BS, or network nodes other than the BS. Theterm ‘eNB’ may be replaced with the term ‘fixed station’, ‘Node B’,‘Base Station (BS)’, ‘access point’, etc. The term ‘UE’ may be replacedwith the term ‘Mobile Station (MS)’, ‘Mobile Subscriber Station (MSS)’,‘mobile terminal’, etc.

The embodiments of the present invention may be achieved by variousmeans, for example, hardware, firmware, software, or a combinationthereof. In a hardware configuration, the methods according to theembodiments of the present invention may be achieved by one or moreApplication Specific Integrated Circuits (ASICs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), Field Programmable Gate Arrays(FPGAs), processors, controllers, microcontrollers, microprocessors,etc.

In a firmware or software configuration, the embodiments of the presentinvention may be implemented in the form of a module, a procedure, afunction, etc. For example, software code may be stored in a memory unitand executed by a processor. The memory unit is located at the interioror exterior of the processor and may transmit and receive data to andfrom the processor via various known means.

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent invention. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of theinvention should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein.

INDUSTRIAL APPLICABILITY

The present invention is applicable to wireless communicationapparatuses such as a UE, a relay, a BS, etc.

What is claimed is:
 1. A method for transmitting an uplink signal by aUser Equipment (UE) according to a HARQ (hybrid automatic repeat andrequest) operation in a wireless communication system supporting carrieraggregation, the method comprising: configuring a first cell to FDD(frequency division duplex) and a second cell to TDD (time divisionduplex); transmitting an initial PUSCH (physical uplink shared channel)in a first subframe of the second cell; receiving a PHICH (physical HARQindicator channel) for the initial PUSCH and a PDCCH (physical downlinkcontrol channel) for a retransmission of the initial PUSCH, in a secondsubframe of the first cell; and transmitting a HARQ retransmission ofthe initial PUSCH in a third subframe of the second cell, according tothe PHICH and the PDCCH received on the first cell.
 2. The method ofclaim 1, wherein the initial PUSCH, the PHICH, the PDCCH and the HARQretransmission correspond to a same HARQ process.
 3. The method of claim1, wherein the first subframe, the second subframe and the thirdsubframe correspond to a same HARQ process.
 4. The method of claim 1,wherein a gap between the first subframe and the second subframe and agap between the second subframe and the third subframe are set accordingto a UL(uplink)-DL(downlink) configuration of the second cell.
 5. Themethod of claim 1, wherein the UE is configured to monitor the firstcell for scheduling the second cell.
 6. A User Equipment (UE) configuredto transmit an uplink signal according to a HARQ (hybrid automaticrepeat and request) operation in a wireless communication systemsupporting carrier aggregation, the UE comprising: a radio frequency(RF) unit; and a processor, wherein the processor is configured toconfigure a first cell to FDD (frequency division duplex) and a secondcell to TDD (time division duplex), to transmit an initial PUSCH(physical uplink shared channel) in a first subframe of the second cell,to receive a PHICH (physical HARQ indicator channel) for the initialPUSCH and a PDCCH (physical downlink control channel) for aretransmission of the initial PUSCH, in a second subframe of the firstcell, and to transmit a HARQ retransmission of the initial PUSCH in athird subframe of the second cell, according to the PHICH and the PDCCHreceived on the first cell.
 7. The UE of claim 6, wherein the initialPUSCH, the PHICH, the PDCCH and the HARQ retransmission correspond to asame HARQ process.
 8. The UE of claim 6, wherein the first subframe, thesecond subframe and the third subframe correspond to a same HARQprocess.
 9. The UE of claim 6, wherein a gap between the first subframeand the second subframe and a gap between the second subframe and thethird subframe are set according to a UL(uplink)-DL(downlink)configuration of the second cell.
 10. The UE of claim 6, wherein the UEis configured to monitor the first cell for scheduling the second cell.